1. Field of the Invention
The invention relates generally to parts handling equipment, and more particularly to an improved electronic circuit board handling and testing apparatus that is adapted to position each of an inventory of identical circuit boards into a test fixture and, subsequent to the completion of a testing protocol, sort each board in accordance with a test result. Multiple machines may be positioned in-line such that all sorted GOOD circuit boards are transported to a single location at the end of the line.
The present invention is particularly adapted for handling and testing of small printed circuit boards, which include one or more memory devices typically referred to as Memory Modules, SIMM boards, DIMM boards, and RIMM boards.
2. Description of Related Art
Single Test Site, Gravity Operation
Known circuit board handlers, such as U.S. Pat. No. 5,704,489 to Smith (xe2x80x9cSmith ""489xe2x80x9d), deposit sorted circuit boards by using gravity and a diverting mechanism to direct boards down one of a pair of exit chutes into a pass or fail bin or containment vessel. A GOOD collection bin and a BAD collection bin are required for each handler. However, high volume production environments may use ten to fifty single site test handlers.
The use of gravity and the diverting mechanism of the Smith patent cause undesired forces to be exerted on the circuit boards as they bounce down the exit chute. The undesired forces can cause damage to components mounted on the circuit boards.
Additionally, forces exerted on boards as they fall into a collection bin from the exit chute can also cause damage to components on the circuit board. Components on circuit boards lying in the collection bin also may be damaged as newly sorted boards are dropped onto them.
Magazine Sleeve, Singulator Mechanism and Adjustable Circuit Probe
Known circuit board handlers, such as disclosed in Smith ""489, typically include magazine sleeves of several sizes, each of which is adapted to accommodate a plurality of circuit boards of corresponding width. The circuit boards are stacked one on top of each other within the magazine sleeve.
The known circuit board handlers, such as Smith ""489, include a singulator mechanism having the magazine sleeves releasably attached directly above the singulator mechanism. The singulator mechanism performs a sequence of steps to drop a single circuit board from the bottom of the stack of boards held in the magazine sleeve. The separated or xe2x80x9csingulatedxe2x80x9d circuit board is dropped from the magazine assembly onto a shelf member of a testing assembly and then pushed into the modular-testing component of the testing assembly. Such circuit board handlers can potentially cause damage to components, due to dropping the entire stack the height of one circuit board. As the entire stack is dropped within the magazine sleeve, relative motion between the circuit boards causes interference between components mounted on the bottom of one board with components mounted on the top of the circuit board stacked immediately adjacent. Additionally, such known circuit board handlers are limited in the number and/or type of tests that may be performed on each circuit board.
Furthermore, the known circuit board handlers can potentially cause damage to components by allowing operators to improperly load the circuit boards into the magazine sleeve. For example, circuit boards may be loaded upside down causing a misalignment of the circuit board contacts with the testing apparatus contacts.
Potential Component Damage, Singulation Sequence, Adjustable Circuit Probe
The singulation sequence, performed on known circuit board handlers, such as Smith ""489, can potentially damage components mounted on the circuit boards. The singulation sequence causes the lowermost circuit board to drop from the bottom of the stack onto a shelf member. The singulation sequence then causes the entire stack to drop the equivalent of the height of one circuit board.
Additionally, the known circuit board handlers can potentially cause damage to components, due to mechanical interference between the singulator mechanism and components mounted near the edge of the circuit board.
Also, the known circuit board handlers can potentially cause damage to components, due to dropping a single circuit board onto the shelf member.
Furthermore, the known circuit board handlers do not reliably control the extension of the singulator block. The singulator blocks in known handlers are screwed onto a cylinder shaft and retained with thread locking adhesive. Inherent problems in this design include variation in the extension of the cylinder shaft, non reusable cylinders due to the thread retaining adhesive, and cylinder bumper wear. These problems result in component damage due to varying upper and lower ledge retainers, such as Smith ""489.
Finally, the known circuit board handlers are limited in what tests they may perform, as well as where circuit boards may be tested.
Modular Test Assembly, Connectors, Adjustable Circuit Probe
The known circuit board handlers utilize a xe2x80x9cZero Insertion Forcexe2x80x9d (ZIF) contact mechanism. The contact fixture uses a set of gold plated, metal fingers, which must be flexed or forced into position to make electrical contact with connector pads on the circuit board under test. The gold plated, metal fingers of the ZIF contact fixture used on known circuit board handlers must be manufactured to a required length to allow for flexing of the fingers to contact the circuit board under test. The required length of the metal fingers is detrimental to higher frequency test signals. Complete testing at high frequency operation is not possible using the metal fingers used on known handlers. Additionally, no tests on the circuit board may be performed outside of the text fixture.
Furthermore, the gold plated, metal fingers of the ZIF contact fixture are susceptible to breaking, are expensive and are manufactured by a single source only.
Therefore, there exists a need in the circuit board handler art for an improved handler that overcomes the above-mentioned problems, and allows at least one additional test to be performed on circuit boards by an adjustable circuit probe.
In accordance with the present invention there is provided a circuit board handling and testing apparatus (i.e., handler), which comprises a housing defining a stationary top surface. Attached to the housing of the present invention are an improved singulating mechanism, an improved magazine assembly, an improved modular test component, a new conveyor transport assembly, and an adjustable circuit probe for performing additional testing.
In a preferred embodiment of the present invention, the new conveyor transport mechanism is mounted directly below a pivotal shelf member, which is used to eject circuit boards from a testing assembly and/or adjustable circuit probe. The conveyor transport extends out of the sides, beyond a housing of the handler. This allows individual machines, built in accordance with the present invention, to be installed next to each other and transport sorted GOOD circuit boards from one machine through multiple machines in a line to a single destination, instead of individual bins at each machine.
The conveyor transport and the unique workings of a fail tray included in the present invention eliminate the use of a divert mechanism, such as disclosed in the Smith ""489 patent, thus eliminating risk of damage to components during the sorting process.
The improved magazine assembly uses precision guide rails to hold stacked circuit boards in relative position thus minimizing risk of damage to components mounted on the circuit boards.
The materials and design of the singulating mechanism of the present invention have been improved for increased reliability of the singulation process and minimized risk of damage to components mounted on the circuit boards. In the preferred embodiment of the present invention, the modular test assembly has been improved to accommodate a wider range of test connectors thus allowing test systems to test the circuit boards at higher frequencies.
The addition of an adjustable circuit probe, between a magazine and a modular test assembly, allows the present invention to perform additional testing of circuit boards.
The improvements regarding the magazine sleeve, the singulator mechanism, the modular test assembly and the adjustable circuit probe of the present invention are also useful on known handlers.